The present invention relates to a side airbag device, and in particular, relates to a side airbag device that is provided at a seat back of a seat for a vehicle.
Conventionally, various types of side airbag device that can protect an occupant in the vehicle with an airbag inflated by gas supplied from an inflator at a vehicle side crash or a vehicle turnover have been proposed.
US Patent Application Publication No. 2004/0130127 A1 discloses an airbag device for a vehicle side crash, in which an airbag that is partitioned into its lower chamber and its upper chamber by a seam is provided at an outer side of a seat back of a seat. In this airbag device, when there occurs the vehicle side crash or the vehicle overturn, a gas generator (inflator) generates and supplies gas into the lower and upper chambers, thereby the respective chambers are inflated, so that the airbag can be inflated along a window side of the seat. Herein, a larger volume of gas with a higher pressure gas is supplied into the lower chamber compared to gas supplied to the upper chamber. Accordingly, since the lower chamber is inflated earlier, it can receive a waist of the occupant properly by moving it laterally. Meanwhile, since the upper chamber is inflated by the gas with a lower pressure, it can receive an upper body of the occupant softly.
Japanese Patent Laid-Open Publication No. 2005-186891 discloses a side airbag device, in which an airbag includes an upper airbag chamber to protect a chest and a abdomen of the occupant and a lower airbag chamber to protect a waist of the occupant. Herein, this airbag has a sewing portion to control a pressure difference between both chambers to a specified desired value, and, an inner pressure of the lower airbag chamber is adjusted to be higher than that of the upper airbag chamber. Thus, the lower airbag chamber of this side airbag device is also configured so as to be inflated earlier than the upper airbag chamber.
The conventional airbag devices disclosed in the above-described patent publications may be superior in protecting a whole part of the occupant's side body with the upper chamber (upper airbag chamber) for softly protecting the occupant's chest and abdomen and with the lower chamber (lower airbag chamber) for receiving the occupant's waist by moving it laterally. However, these airbag devices may perform its superior function for the occupant that has a relatively large body size, but it could not necessarily provide its proper protection to the occupant that has a relatively small or middle body size (such as a female driver). This is because the upper chamber (upper airbag chamber) is located at a portion where an upper arm of the occupant having the relatively small or middle body size is positioned, so the occupant's upper arm is pushed by this upper chamber with its relatively high gas pressure. This pushing would cause an uncomfortable feeling to the occupant having the relatively small or middle body size. The occupant would feel uncomfortable in its upper arm or its side body.
It is preferable to inflate the airbag with the higher pressure from perspectives of receiving the occupant's waist properly by moving it laterally and obtaining a prompt (earlier) inflation of the airbag. To the contrary, however, this higher pressurization would deteriorate the above-described uncomfortable feeling that the occupant may have. No conventional side airbag device that may solve this problem effectively to provide the proper protection at the vehicle side crash or the overturn regardless of the body size of the occupant has been proposed yet.